Intermediate anchorage for concrete structures

ABSTRACT

An intermediate anchor having a wedge hole is placed at a concrete construction joint. A sheathed tendon is inserted through the intermediate anchor. Following setting of concrete poured on a bearing side of the concrete construction joint, the sheathing of the tendon is cut circumferentially around the tendon in a wedge hole of the tendon. The sheathed tendon is then tensioned. This tensioning creates an exposed portion of the tendon in the wedge hole. A tension holding wedge is placed in the wedge hole so as to grip the exposed portion to hold the tension. Seals on the bearing side and a stressing side of the concrete construction joint seals the exposed portion.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to intermediate anchorages for theunbonded post-tensioning tendons used to reinforce concrete slabs andother concrete structures.

BACKGROUND OF THE INVENTION

[0002] Concrete slabs and other structures are used to form floors,walls, and other elements of buildings. Each such concrete structure istypically reinforced by placing an unbonded post-tensioning tendon in aform (usually a wood form) prior to pouring of the concrete and thentensioning the tendon after the concrete has been poured into the formand has set. This reinforcement permits the concrete structure to beargreater loads than would otherwise be the case.

[0003] The tendon is composed of a greased high strength steel cablecontained within a sheathing. Additionally, the tendon is usuallyprovided with two terminal anchors, one at each end of the concretestructure that is to be reinforced. The tendon is installed in the formand the concrete is poured and allowed to set. The tendon is thentensioned, and the tension on the tendon is locked off at the terminalanchors. In corrosive environments such as parking garages, corrosionprotection is used to protect the tendon and the anchors. Accordingly,it is known to provide sleeves and seals behind the terminal anchors andcaps and seals on the frontsides of the terminal anchors.

[0004] When concrete slabs and other structures are so large that theyrequire two or more pours, intermediate anchors between the terminalanchors are added to the tendon at the construction joint between thedifferent pours. In order to install an intermediate anchor, theintermediate anchor is positioned at the construction joint and thefirst pour of concrete is made. After this concrete has set, sheathingis stripped from the tendon on the frontside of the intermediate anchorso as to expose a long portion of the cable. A jack is applied so thatit grips this exposed portion with wedges (tensioning grippers) and isoperated to tension the tendon. A wedge is then installed in theintermediate anchor so that it grips the cable where the sheathing hasbeen stripped away to thereby hold the tension. The length of sheathingthat is stripped away is typically equal to the length of the jack and,therefore, a long length of the cable is exposed.

[0005] As in the case of the terminal anchors, corrosion is also aproblem where intermediate anchors are used because, even though theintermediate anchor is buried in concrete, concrete is porous allowingwater to carry corrosive chemicals such as salt to the portion of thetendon that has been stripped of sheathing. Therefore, the tendon at theintermediate anchor must also be provided with corrosion protection.

[0006] This corrosion protection is traditionally provided by coveringthe stripped portion of the tendon on the backside of the intermediateanchor with a split plastic tube or a long solid plastic tube with splitseals. Split seals are also provided on the frontside of theintermediate anchor in an attempt to connect back to the sheathing.However, these traditional corrosion protection systems do not provideadequate corrosion protection.

[0007] The present invention is directed to a sealing arrangement andmethod for use in connection with an intermediate anchor that overcomesone or more of the problems of the prior art.

SUMMARY OF THE INVENTION

[0008] In accordance with one aspect of the present invention, a methodcomprises the following: (i) placing an intermediate anchor having awedge hole at a concrete construction joint; (ii) inserting a tendonthrough the intermediate anchor leaving a sheathing of the tendonsubstantially intact; (iii) making a single cut circumferentially aroundthe sheathing inside the wedge hole; (iv) tensioning the sheathed tendonfollowing setting of concrete poured on a bearing side of the concreteconstruction joint, whereby the tensioning causes the sheathing to pullaway from the single cut so as to thereby create an exposed portion ofthe tendon; and, (v) gripping the exposed portion with a wedge to holdthe tension.

[0009] In accordance with another aspect of the present invention, anintermediate anchor system for a tendon comprises an intermediate anchorand backside and frontside seals. The intermediate anchor has abackside, a frontside, and a wedge hole arranged to receive a wedge. Thebackside and frontside seals are at the backside and the frontside,respectively, of the intermediate anchor. The backside and frontsideseals are arranged to seal an exposed portion of the tendon within thewedge hole, and the exposed portion of the tendon is confined to thewedge hole.

[0010] In accordance with still another aspect of the present invention,an intermediate anchor system comprises a tendon, an intermediateanchor, a wedge, a backside seal, and a frontside seal. The tendon has agreased cable within a sheathing, the tendon has an exposed portion, andthe exposed portion has no sheathing. The intermediate anchor having abackside, a frontside, and a wedge hole arranged to receive a wedge. Thesheathed tendon extends through the intermediate anchor so that theexposed portion is within the wedge hole. The wedge is within the wedgehole and is clamped to the exposed portion of the sheathed tendon. Thebackside seal engages the sheathed tendon at the backside of theintermediate anchor. The frontside seal engages the sheathed tendon atthe frontside of the intermediate anchor. The backside and frontsideseals seal the exposed portion of the sheathed tendon.

[0011] In accordance with yet another aspect of the present invention, amethod comprises the following: (i) placing an intermediate anchorhaving a wedge hole at a concrete construction joint; (ii) inserting atendon through the intermediate anchor leaving a sheathing of the tendonsubstantially intact; (iii) sealing the intermediate anchor on a bearingside of the concrete construction joint; (iv) making a cutcircumferentially around the sheathing in the wedge hole; (v) tensioningthe sheathed tendon following setting of concrete poured on the bearingside of the concrete construction joint, thereby creating an exposedportion of the tendon; (vi) gripping the exposed portion with a wedge tohold the tension; and, (vii) sealing the intermediate anchor on astressing side of the concrete construction joint.

[0012] In accordance with a further aspect of the present invention, anintermediate anchor is provided to anchor a tendon in concrete. Thetendon has an outside diameter. The intermediate anchor has an O-ring toprovide a seal between the intermediate anchor and the tendon, and theO-ring has an inside diameter. The inside diameter of the O-ring issufficiently larger than the outside diameter of the tendon in order topermit the O-ring to move freely over the tendon during installation.

BRIEF DESCRIPTION OF THE DRAWING

[0013] These and other features and advantages of the present inventionwill become more apparent from a detailed consideration of the inventionwhen taken in conjunction with the single FIGURE of the drawing which isa partially sectioned side view of a tendon and an intermediate anchorsystem according to at least one embodiment of the present invention.

DETAILED DESCRIPTION

[0014] An intermediate anchor system 10 according to one embodiment ofthe present invention is shown in the drawing. The intermediate anchorsystem 10 includes an anchor main body 12 (usually a ductile ironcasting) and a cover 14 (usually a plastic coating) together forming anencapsulated intermediate anchor 16. The cover 14 has a neck 18 on abackside of the encapsulated intermediate anchor 16. The neck 18receives a neck 20 of an adaptor 22. The neck 20 of the adaptor 22 hasan external rib 24 that is formed around its perimeter and that mateswith an internal recess 26 of the neck 18 so that the adaptor 22 ispositively coupled to the encapsulated intermediate anchor 16 of theintermediate anchor system 10. The adaptor 22 also has an internallythreaded portion 28 that receives a backside O-ring seal 30 and anexternally threaded backside bushing 32.

[0015] The encapsulated intermediate anchor 16, the adaptor 22, thebackside O-ring seal 30, and the externally threaded backside bushing 32are located on a bearing side 34 of a construction joint 36.Accordingly, during installation of the intermediate anchor system 10,the encapsulated intermediate anchor 16 is suitably attached to a form37 such as by nailing it to the form 37 at the construction joint 36. Atendon 38 is inserted through the externally threaded backside bushing32, the backside O-ring seal 30, the adaptor 22, and the encapsulatedintermediate anchor 16, and is placed in the form 37 so that, when theconcrete is poured into the form 37 during a first pour on the bearingside 34, the tendon 38 will have its proper location. The tendon 38 istypically composed of a plastic sheathed high strength steel cable thatis greased inside of the plastic sheathing.

[0016] The adaptor 22 is affixed to the encapsulated intermediate anchor16 by inserting the neck 20 into the neck 18 until the external rib 24snaps into the recess internal recess 26 of the neck 18. The externallythreaded backside bushing 32 is then threaded into the adaptor 22 untilthe backside O-ring seal 30 is forced into sealing engagement with thetendon 38 and the adaptor 22. Accordingly, the backside O-ring seal 30together with the adaptor 22 and the tendon 38 seals the encapsulatedintermediate anchor 16 on the bearing side 34 of the construction joint36. A secondary O-ring 30 a provides a seal between the adapter 22 andthe neck 18 of the encapsulated intermediate anchor 16.

[0017] An open cap 40 is applied to a frontside of the encapsulatedintermediate anchor 16 and has a rib 42 around an external perimeter ofthe open cap 40. The encapsulated intermediate anchor 16 has acomplementary rib 44 around an internal perimeter thereof. The open cap40 has an internally threaded portion 46 that threadably engages anexternally threaded frontside bushing 48. The open cap 40, theexternally threaded frontside bushing 48, and an O-ring 50 are placed onthe tendon 38, but are not engaged to one another until tensioning ofthe tendon 38 on the bearing side 34 is complete. To permit the O-ring50 to move easily over the tendon 38, the inner diameter of the O-ring50 is at least somewhat larger than the outer diameter of the tendon 38.This feature is important because intermediate anchors are applied totendons off-site and the tendons with their corresponding intermediateanchors mounted thereon are then moved to the site for finalinstallation. Therefore, it is frequently necessary to move intermediateanchors over long runs of their tendons which could damage the O-ringsif the O-rings cannot move freely over their tendons.

[0018] Concrete may then be poured on the bearing side 34 of theconstruction joint 36. A pocket former may be applied to theencapsulated intermediate anchor 16 prior to pouring of the concrete inorder to prevent concrete from flowing into a wedge hole 52 of theencapsulated intermediate anchor 16. After pouring, this pocket formermay then be removed.

[0019] Once the concrete sets on the bearing side 34, a circumferentialcut is made around the sheathing of the tendon 38 within the wedge hole52 of the encapsulated intermediate anchor 16. The tendon 38 is thentensioned by placing the nose of a hydraulic jack against theencapsulated intermediate anchor 16 on a stressing side 54 of theconstruction joint 36. A gripper wedge 56 is placed on the tendon 38 atthe opposing end of the hydraulic jack so that the gripper wedge 56penetrates the sheathing of the tendon 38 and engages the steel cablewithin the sheathing. The tendon 38 is tensioned with the gripper wedge56 by use of the jack.

[0020] During tensioning, the steel cable of the tendon 38 stretches.Because the sheathing is bonded to the cured concrete on the bearingside 34, the sheathing of the tendon 38 in the wedge hole 52 will openas the steel cable stretches, thereby creating an exposed portion 58 inthe sheathing. After a proper amount of tensioning has been applied tothe tendon 38, a permanent wedge 60 surrounding the exposed portion 58of the tendon 38 is placed into the wedge hole 52 of the encapsulatedintermediate anchor 16. When the jack is released, force is transferredfrom the gripper wedge 56 to the permanent wedge 60 so as to lock offthe tension in the tendon 38 on the bearing side 34 of the constructionjoint 36.

[0021] The open cap 40 is then attached to the encapsulated intermediateanchor 16 so that the rib 42 is captured by the corresponding rib 44 tothereby lock the open cap 40 onto the encapsulated intermediate anchor16 and to thereby compress a gasket 61 to form a seal between the opencap 40 and the encapsulated intermediate anchor 16. The externallythreaded frontside bushing 48 is threaded into the internally threadedportion 46 until the frontside O-ring seal 50 is biased against thetendon 38 and against the internally threaded portion 46 of the open cap40 to form a seal around the tendon 38 to thereby seal the encapsulatedintermediate anchor 16 on the stressing side 54 of the constructionjoint 36.

[0022] Also, the gripper wedge 56 penetrates the sheathing duringtensioning of the tendon 38, thereby damaging the sheathing at thatlocation. This damaged portion of the sheathing may be repaired such asby taping so as to restore the integrity of the sheathing.

[0023] Accordingly, the exposed portion 58 of the tendon 38 is sealed bythe encapsulated intermediate anchor 16, the adaptor 22, the backsideO-ring seal 30, and the externally threaded backside bushing 32 on thebearing side 34 of the construction joint 36, and by the encapsulatedintermediate anchor 16, the open cap 40, the frontside O-ring seal 50,and the externally threaded frontside bushing 48 on the stressing side54 of the construction joint 36. Thereafter, concrete may be poured intothe form 37 during a second pour on the stressing side 54.

[0024] Certain modifications of the present invention will occur tothose practicing in the art of the present invention. Accordingly, thedescription of the present invention is to be construed as illustrativeonly and is for the purpose of teaching those skilled in the art thebest mode of carrying out the invention. The details may be variedsubstantially without departing from the spirit of the invention, andthe exclusive use of all modifications which are within the scope of theappended claims is reserved.

What is claimed is:
 1. A method comprising: placing an intermediateanchor having a wedge hole at a concrete construction joint; inserting atendon through the intermediate anchor leaving a sheathing of the tendonsubstantially intact; making a single cut circumferentially around thesheathing inside the wedge hole; tensioning the sheathed tendonfollowing setting of concrete poured on a bearing side of the concreteconstruction joint, whereby the tensioning causes the sheathing to pullaway from the single cut so as to thereby create an exposed portion ofthe tendon; and, gripping the exposed portion with a wedge to hold thetension.
 2. The method of claim 1 wherein the tensioning of the sheathedtendon comprises applying a gripper wedge to the tendon outside of theintermediate anchor.
 3. The method of claim 2 wherein application of thegripper wedge damages the sheathing of the tendon, and wherein themethod further comprises repairing the damage before pouring concrete ona stressing side of the concrete construction joint.
 4. The method ofclaim 3 wherein the repairing of the damage comprises taping.
 5. Themethod of claim 1 further comprising attaching an adaptor to theintermediate anchor on the bearing side and inserting an O-ring withinthe adaptor so as to engage the adaptor and the tendon.
 6. The method ofclaim 5 further comprising attaching a bushing to the adaptor so as tobias the O-ring into sealing engagement with the adaptor and the tendon.7. The method of claim 1 further comprising attaching a cap to theintermediate anchor on a stressing side of the construction joint andinserting an O-ring within the cap to engage the cap and the tendon. 8.The method of claim 7 further comprising attaching a bushing to the capso as to bias the O-ring into sealing engagement with the cap and thetendon.
 9. The method of claim 7 wherein the O-ring has an innerdiameter larger than an outer diameter of the tendon.
 10. The method ofclaim 1 further comprising: attaching an adaptor to the intermediateanchor on the bearing side; attaching a backside bushing to the adaptor;attaching a cap to the intermediate anchor on a stressing side of theconstruction joint; and, attaching a frontside bushing to the cap. 11.The method of claim 10 further comprising: inserting a backside O-ringwithin the adaptor so as to engage the adaptor and the tendon; and,inserting a frontside O-ring within the cap so as to engage the cap andthe tendon.
 12. An intermediate anchor system for a tendon comprising:an intermediate anchor having a backside, a frontside, and a wedge holearranged to receive a wedge; and, backside and frontside seals at thebackside and the frontside, respectively, of the intermediate anchor,wherein the backside and frontside seals are arranged to seal an exposedportion of the tendon within the wedge hole, and wherein the exposedportion of the tendon is confined to the wedge hole.
 13. Theintermediate anchor system of claim 12 wherein the backside sealcomprises an adaptor engaging the intermediate anchor and an O-ringengaging the adaptor and the tendon.
 14. The intermediate anchor systemof claim 13 wherein the backside seal further comprises a bushingbiasing the O-ring into sealing engagement with the adaptor and thetendon.
 15. The intermediate anchor system of claim 12 wherein thefrontside seal comprises a cap engaging the intermediate anchor and anO-ring engaging the cap and the tendon.
 16. The intermediate anchorsystem of claim 15 wherein the frontside seal further comprises abushing biasing the O-ring into sealing engagement with the cap and thetendon.
 17. The intermediate anchor system of claim 15 wherein theO-ring has an inner diameter at least somewhat larger than an outerdiameter of the tendon.
 18. The intermediate anchor system of claim 12wherein the backside seal comprises an adaptor engaging the intermediateanchor and a backside O-ring engaging the adaptor and the tendon, andwherein the frontside seal comprises a cap engaging the intermediateanchor and a frontside O-ring engaging the cap and the tendon.
 19. Theintermediate anchor system of claim 18 wherein the backside seal furthercomprises a backside bushing biasing the backside O-ring into sealingengagement with the adaptor and the tendon, and wherein the frontsideseal further comprises a frontside bushing biasing the frontside O-ringinto sealing engagement with the cap and the tendon.
 20. Theintermediate anchor system of claim 12 wherein the frontside sealcomprises: a cap engaging the intermediate anchor; an O-ring within thecap and engaging both the cap and the tendon; and, a bushing engagingthe cap so as to bias the O-ring into sealing engagement with the capand the tendon.
 21. The intermediate anchor system of claim 12 whereinthe backside seal is on a bearing side of the intermediate anchorsystem, and wherein the backside seal comprises: an adaptor having anadaptor neck engaging an anchor neck of the intermediate anchor; anO-ring within the adaptor and engaging both the adaptor and the tendon;and, a bushing engaging the adaptor so as to bias the O-ring intosealing engagement with the adaptor and the tendon.
 22. The intermediateanchor system of claim 21 wherein the O-ring is a backside O-ring,wherein the bushing is a backside bushing, and wherein the frontsideseal comprises: a cap engaging the intermediate anchor; a frontsideO-ring within the cap and engaging both the cap and the tendon; and, afrontside bushing engaging the cap so as to bias the frontside O-ringinto sealing engagement with the cap and the tendon.
 23. Theintermediate anchor system of claim 12 wherein the backside seal is on abearing side of the intermediate anchor system, and wherein the backsideseal comprises an adaptor and a bushing engaging one another.
 24. Theintermediate anchor system of claim 23 wherein the backside seal furthercomprises an O-ring biased into sealing engagement with the adaptor andthe tendon when the adaptor and the bushing engage one another.
 25. Anintermediate anchor system comprising: a tendon having a greased cablewithin a sheathing, wherein the tendon has an exposed portion, andwherein the exposed portion has no sheathing; an intermediate anchorhaving a backside, a frontside, and a wedge hole arranged to receive awedge, wherein the sheathed tendon extends through the intermediateanchor so that the exposed portion is within the wedge hole; a wedgewithin the wedge hole and clamped to the exposed portion of the sheathedtendon; a backside seal engaging the sheathed tendon at the backside ofthe intermediate anchor; and, a frontside seal engaging the sheathedtendon at the frontside of the intermediate anchor, wherein the backsideand frontside seals seal the exposed portion of the sheathed tendon. 26.The intermediate anchor system of claim 25 wherein the backside sealcomprises an adaptor engaging the intermediate anchor and an O-ringengaging the adaptor and the tendon.
 27. The intermediate anchor systemof claim 26 wherein the backside seal further comprises a bushingbiasing the O-ring into sealing engagement with the adaptor and thetendon.
 28. The intermediate anchor system of claim 25 wherein thefrontside seal comprises a cap engaging the intermediate anchor and anO-ring engaging the cap and the tendon.
 29. The intermediate anchorsystem of claim 28 wherein the frontside seal further comprises abushing biasing the O-ring into sealing engagement with the cap and thetendon.
 30. The intermediate anchor system of claim 28 wherein theO-ring has an inner diameter larger than an outer diameter of thetendon.
 31. The intermediate anchor system of claim 25 wherein thebackside seal comprises an adaptor engaging the intermediate anchor anda backside O-ring engaging the adaptor and the tendon, and wherein thefrontside seal comprises a cap engaging the intermediate anchor and afrontside O-ring engaging the cap and the tendon.
 32. The intermediateanchor system of claim 31 wherein the backside seal further comprises abackside bushing biasing the backside O-ring into sealing engagementwith the adaptor and the tendon, and wherein the frontside seal furthercomprises a frontside bushing biasing the frontside O-ring into sealingengagement with the cap and the tendon.
 33. The intermediate anchorsystem of claim 25 wherein the backside seal comprises: an adaptorengaging the intermediate anchor; an O-ring within the adaptor andengaging both the adaptor and the tendon; and, a bushing engaging theadaptor so as to bias the O-ring into sealing engagement with theadaptor and the tendon.
 34. The intermediate anchor system of claim 33wherein the O-ring is a backside O-ring, wherein the bushing is abackside bushing, and wherein the frontside seal comprises: a capengaging the intermediate anchor; a frontside O-ring within the cap andengaging both the cap and the tendon; and, a frontside bushing engagingthe cap so as to bias the frontside O-ring into sealing engagement withthe cap and the tendon.
 35. The intermediate anchor system of claim 25wherein the frontside seal comprises: a cap engaging the intermediateanchor; an O-ring within the cap and engaging both the cap and thetendon; and, a bushing engaging the cap so as to bias the O-ring intosealing engagement with the cap and the tendon.
 36. A method comprising:placing an intermediate anchor having a wedge hole at a concreteconstruction joint; inserting a tendon through the intermediate anchorleaving a sheathing of the tendon substantially intact; sealing theintermediate anchor on a bearing side of the concrete constructionjoint; making a cut circumferentially around the sheathing in the wedgehole; tensioning the sheathed tendon following setting of concretepoured on the bearing side of the concrete construction joint, therebycreating an exposed portion of the tendon; gripping the exposed portionwith a wedge to hold the tension; and, sealing the intermediate anchoron a stressing side of the concrete construction joint.
 37. The methodof claim 36 wherein the sealing of the intermediate anchor on thebearing side of the concrete construction joint comprises attaching anadaptor to the intermediate anchor on the bearing side and inserting anO-ring within the adaptor so as to engage the adaptor and the tendon.38. The method of claim 37 wherein the sealing of the intermediateanchor on the bearing side of the concrete construction joint furthercomprises attaching a bushing to the adaptor so as to bias the O-ringinto sealing engagement with the adaptor and the tendon.
 39. The methodof claim 36 wherein the sealing of the intermediate anchor on thestressing side of the concrete construction joint comprises attaching acap to the intermediate anchor on the stressing side and inserting anO-ring within the cap to engage the cap and the tendon.
 40. The methodof claim 39 wherein the sealing of the intermediate anchor on thestressing side of the concrete construction joint further comprisesattaching a bushing to the cap so as to bias the O-ring into sealingengagement with the cap and the tendon.
 41. The method of claim 36wherein the sealing of the intermediate anchor on the bearing andstressing sides of the concrete construction joint comprises: attachingan adaptor to the intermediate anchor on the bearing side and insertinga backside O-ring within the adaptor so as to engage the adaptor and thetendon; and, attaching a cap to the intermediate anchor on the stressingside and inserting a frontside O-ring within the cap so as to engage thecap and the tendon.
 42. The method of claim 41 further comprising:attaching a backside bushing to the adaptor so as to bias the backsideO-ring into sealing engagement with the adaptor and the tendon; and,attaching a frontside bushing to the cap so as to bias the frontsideO-ring into sealing engagement with the cap and the tendon.
 43. Themethod of claim 36 wherein the sealing of the intermediate anchor on thebearing side of the concrete construction joint comprises: attaching anadaptor having an adaptor neck to an anchor neck of the intermediateanchor; inserting an O-ring within the adaptor so as to engage both theadaptor and the tendon; and, engaging a bushing to the adaptor so as tobias the O-ring into sealing engagement with the adaptor and the tendon.44. The method of claim 36 wherein the sealing of the intermediateanchor on the stressing side of the concrete construction jointcomprises: attaching a cap to the intermediate anchor; inserting anO-ring within the cap so as to engage both the cap and the tendon; and,engaging a bushing to the cap so as to bias the O-ring into sealingengagement with the cap and the tendon.
 45. The method of claim 36wherein the sealing of the intermediate anchor on the bearing andstressing sides of the concrete construction joint comprises: attachingan adaptor having an adaptor neck to an anchor neck of the intermediateanchor on the bearing side; inserting a backside O-ring within theadaptor so as to engage both the adaptor and the tendon; engaging abackside bushing to the adaptor so as to bias the backside O-ring intosealing engagement with the adaptor and the tendon; attaching a cap tothe intermediate anchor on the stressing side; inserting a frontsideO-ring within the cap so as to engage both the cap and the tendon; and,engaging a frontside bushing to the cap so as to bias the frontsideO-ring into sealing engagement with the cap and the tendon.
 46. Themethod of claim 36 wherein the tensioning of the sheathed tendoncomprises applying a jack and a gripper wedge to the tendon.
 47. Themethod of claim 36 wherein the sealing of the intermediate anchor on thebearing side of the concrete construction joint comprises: attaching anadaptor to the intermediate anchor on the bearing side; and, engaging abushing to the adaptor.
 48. The method of claim 36 wherein the sealingof the intermediate anchor on the bearing and stressing sides of theconcrete construction joint comprises: attaching an adaptor to theintermediate anchor on the bearing side; engaging a backside bushing tothe adaptor; attaching a cap to the intermediate anchor on the stressingside; and, engaging a frontside bushing to the cap.
 49. The method ofclaim 36 wherein the tensioning of the sheathed tendon damages thesheathing of the tendon, and wherein the method further comprisesrepairing the damage before pouring concrete on the stressing side ofthe concrete construction joint.
 50. The method of claim 49 wherein therepairing of the damage comprises taping.
 51. An intermediate anchor foranchoring a tendon in concrete, the tendon having an outside diameter,the intermediate anchor having an O-ring to provide a seal between theintermediate anchor and the tendon, the O-ring having an insidediameter, the inside diameter of the O-ring being sufficiently largerthan the outside diameter of the tendon in order to permit the O-ring tomove freely over the tendon during installation.